This section provides background information related to the present disclosure, which is not necessarily prior art.
Vehicle engines often include a liquid cooling system, which circulates coolant through pipes and passageways in the engine in order to regulate temperature of the engine. As the coolant is circulated through a warm engine, it absorbs heat in order to cool the engine. After the coolant exits the engine, it passes through a heat exchanger, or radiator, which transfers heat from the coolant to air blowing through the heat exchanger. Typical combustion engines run most efficiently when the coolant is about 200° F. (93° C.). At this optimal temperature, the engine's combustion chamber is warm enough to completely vaporize fuel, thereby optimizing combustion and reducing emissions.
During a cold engine start, the coolant is typically below this optimal temperature, which may undesirably result in reduced fuel economy and increased engine wear. Thus, onboard thermal energy storage systems exist for maintaining coolant at a predetermined temperature. While current onboard thermal energy storage systems are suitable for their intended use, they are subject to improvement. The present teachings advantageously provide for coolant thermal energy storage systems and methods that are more efficient, do not add weight, complexity, or cost to the vehicle, and provide increased fuel economy/emissions benefits over onboard thermal energy storage systems.